Fix potential-bashisms in monitor_dd_progress

As suggested by Carl [1],
> /usr/lib/dracut/modules.d/99kdumpbase/monitor_dd_progress has some
> inconsistencies with other scripts in that directory.  It is missing the
> .sh extension and is not executable.  The latter is resulting in an
> rpmlint error.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=2239566#c2

Suggested-by: Carl George <carl@redhat.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
Reviewed-by: Philipp Rudo <prudo@redhat.com>
Reviewed-by: Dave Young <dyoung@redhat.com>

dracut-kdump.sh

@@ -377,7 +377,7 @@ dump_raw()
 	if ! echo "$CORE_COLLECTOR" | grep -q makedumpfile; then
 		_src_size=$(stat --format %s /proc/vmcore)
 		_src_size_mb=$((_src_size / 1048576))
-		/kdumpscripts/monitor_dd_progress $_src_size_mb &
+		/kdumpscripts/monitor_dd_progress.sh $_src_size_mb &
 	fi
 
 	dinfo "saving vmcore"

dracut-module-setup.sh

@@ -1020,8 +1020,7 @@ install() {
         kdump_install_random_seed
     fi
     dracut_install -o /etc/adjtime /etc/localtime
-    inst "$moddir/monitor_dd_progress" "/kdumpscripts/monitor_dd_progress"
-    chmod +x "${initdir}/kdumpscripts/monitor_dd_progress"
+    inst "$moddir/monitor_dd_progress.sh" "/kdumpscripts/monitor_dd_progress.sh"
     inst "/bin/dd" "/bin/dd"
     inst "/bin/tail" "/bin/tail"
     inst "/bin/date" "/bin/date"